The adsorption and gas-phase or surface diffusion properties of a series of microporous pellets made by the compaction of very fine graphite powder were reported. The overall degree of compaction of the powder was very nearly the same in all cases, but the mode of compaction was varied. The resulting variation in the macroscopic structural inhomogeneity of the pellets (examined in some detail in a parallel study) was shown to affect both adsorption and diffusion properties. The effect on adsorption properties was modest but definite and could be accounted for by the dependence of the extent of adsorption on pore size. On the other hand, the experimental gas-phase and surface diffusion coefficients were strongly dependent on macroscopic structure. The dependence of the surface diffusion coefficient was particularly marked and was of special interest: such effects have not, so far, been taken into account in interpretations of experimental data, although they could be predicted theoretically. Previous analyses of the structure dependence of experimental gas-phase and surface diffusion coefficients were thus subject to revision in the light of the present conclusions.

Adsorption and Diffusion of Dilute Gases in Microporous Graphite Pellets in Relation to Their Macroscopic Structure. Savvakis, C., Tsimillis, K., Petropoulos, J.H.: Journal of the Chemical Society, Faraday Transactions - 1, 1982, 78[10], 3121-30